The intention of the present invention is to establish a new assembling system for constructing large span buildings formed of composite vertical load-bearing wall-panels and composite floors whereby lateral bracing and stability of the structure is achieved using slender wall and floor elements only, needing no additional stabilizing construction. As a final task there was a challenge to construct the clear, large-span building with plane inner and outer surfaces, containing no ordinary beams and columns extending out of them. How it is done is described in following disclosure of the invention.
It is of importance to emphasize that the present invention relates to large-span, low-rise buildings (of about 20 to 30 m span, up to 15 m height), intended mainly for constructing industrial and similar buildings to which many similar wall-panel systems, in present state of art have never been applied. In most common practice of constructing low-rise concrete buildings of wall-panels the non-bearing curtain walls, requiring additional structural supports, are predominant. Pure wall-panel load-bearing, self-stable, constructions appear very seldom. Some of wall-panel building systems may have more or less similar elements to those of the building system disposed in the present invention but are due to their unreal solutions essentially restricted about being applied to large span buildings. Self-supported structures of load-bearing wall-panels require application of panels having a considerable stiffness, capable of bearing huge vertical loads and horizontal forces ensuring simultaneously stability of the global structure. The main reason why pure wall-panel load-bearing constructions appear so seldom is exactly the stability of the structure which is difficult to be ensured through use of strong panels only. In such a case, panels can not be slender but require significant depth whereby increasing the panel depth increases greatly spend of material which, dependably on height of the building, may become excessive. Too deep wall-panels may become also too weighty or unaesthetic. The depth of the panel, from which the wall panel derives its stiffness, is actually obtained by increasing the distance between the two concrete layers whereby the gap remaining between them has to be filled with some material. Whichever material used to fill the gap makes a significant expense when summarized over large wall areas of the building. Obviously, the depth of the panel has somehow to be increased without spending too much material and that is also one of tasks this invention deals with. But even if increase of the depth of the panel is succeeded in an economic way, getting in that way a stiff load-bearing wall-panel, it still won't be enough to assure stability of the structure when subjected to large vertical and horizontal load and won't decrease enough deflections of panel tops under lateral loads as well as many other requirements of building codes too. The most common large-span-building are constructed of assembled laterally unbraced transversal frames with cantilever-columns or analogously cantilever vertical wall-panels supporting the weighty roof construction so that the vertical cantilever load-bearing columns or panels, having the buckling length twice long as their actual height is, support transversal beams or slab-like roof constructions. Stability of such structures based upon strong laterally unbraced cantilever-columns (or adequate wall-panels) is perhaps the most expensive manner to be paid for stability. Leak of efficient lateral bracing makes such structures unsuitable to be stabilized economically, requiring large cross-sectional dimensions of columns or panels. In accordance with that, the further task of the present invention is to stabilize the structure in some other way lessening in thereby the requirements on panels to be extremely deep. More particularly, what is seek is some transversally braced structure assembled of vertically-placed, load-bearing wall-panels of a moderate depth; whereby stability of the structure is achieved by including all available resources of the structure. Thus, wall-panels could be in that way partially relieved from being the only element which stability is based upon. The manner how it is done is described in disclosure of the invention. Several solutions that I know, may have some partial similarity with the present solution but they were generally neither occupied with the problem of stability nor with applicability to construct real large span buildings. Since the new building system is based upon two solutions whereby the first one seeks to improve the panel and floor unit themselves and the other one relates to the stability of the structure, these two problems will be considered separately.
The most similar solution of the vertically placed, load-bearing wall-panel I know was disclosed by U.S. Pat. No. 4,669,240 written by inventor Giuseppe Amormino. The disclosed patent provides an idea for a load-bearing, sandwich wall-panel which generally suits well the purpose of constructing buildings. But still, the panel contains several weak points which may seriously limit its range of applicability for constructing real large span buildings, as follows. The arrangement of wire mesh reinforcement placed in the middle of the cross-section of each thin concrete layer makes them too flexible. Since the real distribution of axial forces along the panel height is rather eccentric than centric, layers are often subjected to some unavoidable local bending. The reinforcement placed in the middle of the cross section is therefore unsuitable. The present invention introduces a new arrangement of two interspaced layers of mesh reinforcement placed closely to concrete surfaces as will be disclosed. In that way both the panel concrete are significantly strengthened.
The steel rod trusses used in above mentioned application as shear connectors to connect concrete layers, ensuring composite action of the panel, might be not satisfactory rigid for use in higher, slender panels. In such a case there have to be provided many of them. Using of too many trusses requires using of too many smaller pieces of insulating strips, requiring also much more welding, making in that way manufacturing process of the same more time consuming. For that reason, in the present invention the truss connectors are replaced by les pieces of more rigid steel webs which are much stronger, continuously anchored to both the concrete layers. In the same patent, the floor support formed of inner concrete layer being thickened at its top to provide a sufficient bearing surface is awkwardly made for it causes eccentricity. Vertical load, of a great amount is thereby transmitted through such a support causes unnecessary local bending moments, causing permanent stresses in panel elements. Moreover, in such a way the roof/floor is practically supported by one thin inner concrete layer only, having reinforcement placed in the middle. Such load concentrations require more serious supports than presented one. Further deficiency relates to manufacturing of the panel, particularly to the method how the bottom of the mould for the upper concrete layer is temporary fixed to trusses as well as the queer of using a “suitable resin” for bonding fiberglass strips interposed between adjacent pairs of trusses. Final step of filling the “grout or insulation material” into spacing between adjacent insulation strips may be unacceptably time consuming work to do for a quick production. The present invention introduces more efficient way of making panels.
There are many solutions of load-bearing wall-panel as well as many methods of constructing buildings of them in present state of art. However, such building systems are not widely spread in common practice, especially were not applied in large-span low-rise industrial and similar constructions. One of reasons for that is certainly a leak of stability of such buildings that is difficult to be ensured through panels alone, especially when spans are over 20 m and heights of panels exceed 9 m. All solutions for constructing wall-panel buildings that I know do not deal with problems of stability at all.